The formula H2O is also the molecular formula of water. For non-molecular substances such as table salt, we represent the composition with an empirical formula. Sodium chloride is represented by NaCl, meaning that sodium and chlorine ratio in sodium chloride is 1 to 1. Again, the subscript 1 is omitted.
By Phil Myers. The annelids include earthworms, polychaete worms, and leeches. All members of the group are to some extent segmented, in other words, made up of segments that are formed by subdivisions that partially transect the body cavity.Segmentation is also called metamerism.y Phil Myers. The annelids include earthworms, polychaete worms, and leeches. All members of the group are to some extent segmented, in other words, made up of segments that are formed by subdivisions that partially transect the body cavity.
1 They have a circulatory system and a digestive system. 2  Flatworms, roundworms, and segmented worms are all invertebrates. 3  Some species of each type of worm are free-living, meaning they are not dependent on another organism for food. 4  Segmented worms are the most complex animals of these three invertebrates. Students will then continue with their Internet research to compare flatworms, roundworms, and segmented worms by completing the Worm Comparison worksheet. 2  They should use their research to find more information in order to describe how these three types of worms are similar and how they are different.